The present invention relates to a ladder made of a light alloy such as aluminum or the like. Conventionally there have been such a telescopic type of ladders wherein a plurality of rounds are provided between the right and left stanchions which are formed telescopically and both stanchions are extended in use. Also there have been such a folding type of ladders wherein the ladder can be folded in a A-shape at the central region of the stanchions and it is unfolded in use. But these conventional ladders have limitations in their compactification because they should be maintained in a ladder form wherein a plurality of rounds are fixingly provided between both stanchions. In order to transport many ladders to a remote place or to store them for a long time, it is desirable that they can be folded as compactly as possible. But ladders with a folding construction have such defects that the folding portions become weakened in the course of use. Ladders, however, should have sufficient durability as to bear the load exerted thereon when they are used.